Earnings Per Common Share (Earnings Per Common Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Weighted Average Shares:
Weighted average common stock outstanding - basic	956.5	1,035.9
Incremental common shares from assumed exercise or issuance of stock-based awards	6.8	8.5
Weighted average common stock outstanding - diluted	963.3	1,044.4
Net Income (Loss):
Net income (loss)	$ 1,385	$ 1,257
Less: Net income (loss) attributable to noncontrolling interests	4	4
Less: Preferred stock dividends	32	6
Net income (loss) available to MetLife, Inc.’s common shareholders	$ 1,349	$ 1,247
Basic	$ 1.41	$ 1.20
Diluted	$ 1.40	$ 1.19